1. Field of the Invention
The present invention relates to hand exercisers and, in particular, to hand exercisers made with an elastic outer shell having a filler material therein.
2. Description of the Background Art
A variety of hand exercisers are known in the art, such as those made of solid rubber and those made of elastomeric balloons filled with particulate material. Typically, such exercisers are used for physical exercise as well as for mental relaxation and therapeutic use.
Exemplary filled balloon type hand exercisers are the SHARPER IMAGE DEADBALL (TM) and the exerciser described in U.S. Pat. No. 5,350,342 (Scatterday). The SHARPER IMAGE DEADBALL (TM) is similar to that of Scatterday and was on sale prior to the filing date thereof. Scatterday '342 shows an exerciser which is made with a plurality of latex layers 6-14. As discussed on column 3 of the reference, construction of the device involves the following: "P! articulate material and lubricant that make up the core are initially inserted through hole 20 of the first latex layer 6 . . . This procedure is then repeated with the remaining layers . . . Once the core has been inserted in the final layer, glue is placed around the perimeter of hole 20 of layer 14 to fix the latex surrounding the hole to the underlying layer."
Among other problems, the Scatterday type device has problems pertaining to the filler used. Column 3, lines 10 et seq., of Scatterday states: "In practice, seeds such as millet have been used as the particles. As an alternative, the particles can be hard plastic or silicon beads or any other matter that is similar in size and shape to millet and that is hard enough to withstand compressive pressures . . . "
However, seeds such as millet disintegrate over time, damaging and/or altering the functioning thereof. Further, millet has a relatively large size such that its shape is seen through the stretched balloon layers imparting a pocked, or pimpled, appearance to the exerciser.
In addition, millet typically has a tear-like shape and sharp ends which can puncture the balloons. The use of such irregularly shaped particles can damage the balloons. Due to the thinness and the high elasticity of the balloon layers, known balloon filled exercisers have had a tendency to prematurely break or rupture--resulting in the release of particulate material therefrom.
In addition, the prior filler materials have undesirable squeezing characteristics for exercise, therapeutic uses and the like.